TY - JOUR
T1 - Large planets may not form fractionally large moons
AU - Nakajima, Miki
AU - Genda, Hidenori
AU - Asphaug, Erik
AU - Ida, Shigeru
N1 - Funding Information:
We thank David J. Stevenson, John Tarduno, David Kipping, and Alycia Weinberger for the insightful discussion. M.N. was supported in part by the National Aeronautics and Space Administration (NASA) Headquarters under the NASA Earth and Space Science Fellowship Program Grant NNX14AP26H, the Carnegie DTM fellowship, NASA grant numbers 80NSSC19K0514 and 80NSSC21K1184 and Grant-in-Aid for JSPS Fellows JSPS KAKENHI Grant Number 10J09549. Partial funding for M.N. was provided by the Center for Matter at Atomic Pressures (CMAP), a National Science Foundation (NSF) Physics Frontier Center, under Award PHY-2020249. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the National Science Foundation. M.N. was also supported in part by the Alfred P. Sloan Foundation under grant number G202114194. S.I. was supported by JSPS Kakenhi 21H04512. H.G. was supported by MEXT KAKENHI Grant No. JP17H06457. Numerical computations were partly carried out on GRAPE system at Center for Computational Astrophysics, the National Astronomical Observatory of Japan. Figure 6 is created by Michael Franchot.
Publisher Copyright:
© 2022, The Author(s).
PY - 2022/12
Y1 - 2022/12
N2 - One of the unique aspects of Earth is that it has a fractionally large Moon, which is thought to have formed from a Moon-forming disk generated by a giant impact. The Moon stabilizes the Earth’s spin axis at least by several degrees and contributes to Earth’s stable climate. Given that impacts are common during planet formation, exomoons, which are moons around planets in extrasolar systems, should be common as well, but no exomoon has been confirmed. Here we propose that an initially vapor-rich moon-forming disk is not capable of forming a moon that is large with respect to the size of the planet because growing moonlets, which are building blocks of a moon, experience strong gas drag and quickly fall toward the planet. Our impact simulations show that terrestrial and icy planets that are larger than ~1.3−1.6R⊕ produce entirely vapor disks, which fail to form a fractionally large moon. This indicates that (1) our model supports the Moon-formation models that produce vapor-poor disks and (2) rocky and icy exoplanets whose radii are smaller than ~1.6R⊕ are ideal candidates for hosting fractionally large exomoons.
AB - One of the unique aspects of Earth is that it has a fractionally large Moon, which is thought to have formed from a Moon-forming disk generated by a giant impact. The Moon stabilizes the Earth’s spin axis at least by several degrees and contributes to Earth’s stable climate. Given that impacts are common during planet formation, exomoons, which are moons around planets in extrasolar systems, should be common as well, but no exomoon has been confirmed. Here we propose that an initially vapor-rich moon-forming disk is not capable of forming a moon that is large with respect to the size of the planet because growing moonlets, which are building blocks of a moon, experience strong gas drag and quickly fall toward the planet. Our impact simulations show that terrestrial and icy planets that are larger than ~1.3−1.6R⊕ produce entirely vapor disks, which fail to form a fractionally large moon. This indicates that (1) our model supports the Moon-formation models that produce vapor-poor disks and (2) rocky and icy exoplanets whose radii are smaller than ~1.6R⊕ are ideal candidates for hosting fractionally large exomoons.
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U2 - 10.1038/s41467-022-28063-8
DO - 10.1038/s41467-022-28063-8
M3 - Article
C2 - 35105877
AN - SCOPUS:85123972890
VL - 13
JO - Nature Communications
JF - Nature Communications
SN - 2041-1723
IS - 1
M1 - 568
ER -